SPDL1 and non-small cell lung carcinoma: A subgroup analysis highlighted that high levels of sPD-L1 were associated with worse survival in patients affected by NSCLC (HR = 1.81 95%CI: 1.09–3.00, p = 0.02, I2 = 83% for OS; HR = 2.18, 95%CI: 1.27–3.76, p < 0.01, I2 = 88% for PFS).